Metals may be applied to products for both decorative and functional reasons. A metal may be applied to portions of a product, such as a container, a certificate, or a publication to distinguish such portions from other portions that are free of the metal or are printed with non-metallic ink. Metals may also be applied to a substrate to form electrically conductive areas on the substrate such as, for example, traces of an electronic circuit or an imprinted antenna, for example, an antenna for use with a radio-frequency identification transponder.
An image in metal may be formed on a substrate by printing such image with a metallic ink using, for example, gravure, lithographic, and inkjet printing systems. In such printing systems, liquid metallic ink may be applied to the substrate in a manner similar to how non-metallic ink may be applied thereto.
Alternately, a metal image may be formed on the substrate, by coating the substrate indiscriminately with a metal or applying a metal foil to the substrate. Thereafter, portions of the metal or metal foil that are not part of the image may be selectively removed from the substrate by, for example, etching or ablation.
U.S. Pat. No. 5,520,763 discloses transferring foil to a substrate by first selectively applying to the substrate toner particles that have a thermoplastic component. The foil is supplied on a foil strip that includes an adhesive layer facing outwardly, a foil layer, and a release coating on a backing. The foil strip with the adhesive layer and the substrate are introduced into a nip between an impression cylinder and a transfer cylinder. Heat and pressure are applied at the nip to transfer the adhesive and foil from the foil strip to the toner on the substrate to produce a foil printed substrate. The toner on the substrate may be heated before the substrate enters the nip to increase the tackiness thereof.